1. Technical Field
The present invention generally relates to a material handling apparatus and, in an embodiment thereof, more particularly relates to an excavating apparatus, representatively a tracked excavator, having operatively attached to the stick portion of its boom a specially designed combination bucket, breaker, and gripping apparatus which uniquely permits the excavator operator to selectively carry out multiple operations, including digging, breaking refusal material, and object grip and lift tasks without having to change out equipment on the stick.
2. Description of Related Art
Large scale earth excavation operations are typically performed using a powered excavating apparatus, such as a tracked excavator, having an articulated, hydraulically pivotable boom structure with an elongated, pivotal outer end portion commonly referred to as a “stick”. Secured to the outer end of the stick is an excavating bucket, which is hydraulically pivotable relative to the stick between “closed” and “open” positions. By pivotally manipulating the stick, with the bucket swung to a selected operating position, the excavator operator uses the bucket to forcibly dig into the ground, scoop up a quantity of dirt, and move the scooped up dirt quantity to another location, such as into the bed of an appropriately positioned dump truck.
A first common occurrence during conventional digging operations is that the bucket strikes refusal material (in excavation parlance, a material which “refuses” to be dug up) such as rock which simply cannot be broken and scooped up by the bucket. When this occurs, it is typical practice to stop the digging operation, remove the bucket from the stick, and install a hydraulically operated “breaker” on the outer end of the stick in place of the removed bucket. The breaker has, on its outer end, an oscillating tool portion which rapidly hammers the refusal material in a manner breaking it up into portions which can be subsequently dug up. After the breaker has been utilized to break up the refusal material, the operator removes the breaker from the stick, replaces the breaker with the previously removed bucket, and resumes the digging operation with the bucket.
While this procedure is easy to describe, it is a difficult, laborious and time-consuming task for the operator to actually carry out due to the great size and weight of both the bucket and breaker which must be attached to and then removed from the stick, and the necessity for the operator to climb into and out of the high cab area of the excavator (often in inclement weather) to effect each bucket and breaker changeout on the stick. This sequence of bucket/breaker/bucket changeout, of course, must be laboriously repeated each time a significant refusal area is encountered in the overall digging process.
A previously utilized alternative to this single excavator sequence is to provide two excavators for each digging project—one excavator having a bucket attached to its boom stick, and the second excavator having a breaker attached to its boom stick. When the bucket-equipped excavator encounters refusal material during the digging process, it is moved away from the digging site, and the operator climbs down from the bucket-equipped excavator, walks over to and climbs up into the breaker-equipped excavator, drives the breaker-equipped excavator to the digging site, and breaks up the encountered refusal material. Reversing the process, the operator then switches to the bucket-equipped excavator and resumes the digging process to scoop up the now broken-up refusal material.
While this digging/breaking technique is easier on the operator, it is necessary to dedicate two large and costly excavators to a given digging task, thereby substantially increasing the total cost of a given excavation. A modification of this technique is to use two operators one to operate the bucket-equipped excavator, and one to operate the breaker-equipped excavator. This, of course, undesirably increases both the manpower and equipment cost for a given excavation project.
A second common occurrence during conventional digging operations is that removal objects (objects that need to be “removed” or relocated), such as large surface rocks, felled trees, construction debris, and other objects that do not fit into the bucket, need to be removed. When this occurs, it is typical practice to use a specialized excavator that is equipped with a static or hydraulically operated “thumb.” The bucket can be used to position the removal object between the bucket and the thumb for gripping the removal object, lifting and relocating it.
An additional limitation to this configuration is that if the excavator is fitted with a conventional thumb, the thumb presents a second obstacle to the attachment of the breaker. In this instance, a second excavator having a breaker attached to its boom stick is more appropriately required for the digging project. When the bucket and thumb-equipped excavator encounters refusal material during the digging process, it is moved away from the digging site, and the operator climbs down from the bucket-equipped excavator, walks over to and climbs up into the breaker-equipped excavator, drives the breaker-equipped excavator to the digging site, and breaks up the encountered refusal material. Reversing the process, the operator then switches to the bucket and thumb-equipped excavator and resumes the digging process to scoop up the now broken-up refusal material.
Once again, it is necessary to dedicate two large and costly excavators to a given digging task, thereby substantially increasing the total cost of a given excavation project.
An attempt to solve this problem is disclosed in U.S. Pat. No. 6,085,446 and U.S. Pat. No. 4,100,688 for an excavating machine having a motorized milling tool attached to the back of the bucket. A primary disadvantage of these devices is complexity, cost, and reliability. Another disadvantage is the weight that must be continuously carried by the bucket. The additional weight substantially reduces the carrying capacity and mobility of the bucket. Another disadvantage to the device of U.S. Pat. No. 6,085,446 is that the back of the bucket cannot be used to smooth or pad the soil, as is a well-known practice in the industry. Another disadvantage is that surface rock is not subject to an overburden pressure, so it generally fails faster under compression and impact forces than by the shearing forces of a scrapping and gouging rotary drilling tool.
Another attempt to solve this problem is disclosed in U.S. Pat. No. 4,070,772 for an excavating machine having a hydraulic breaker housed inside, or on top of, the boom stick. A primary disadvantage of this device is that it is extremely complex and expensive. Another disadvantage of this device is that it cannot be retrofit to existing excavators. Another disadvantage of this device is that the size of the breaker is limited. Another disadvantage of this device is that the bucket must be fully stowed to access the breaker and vice versa, making simultaneous operation impractical.
A more recent attempt to solve this problem is disclosed in U.S. Pat. No. 5,689,905 for another excavating machine having a hydraulic breaker housed inside, or on top of, the boom stick. In this device, the cutting tool portion (such as a chisel) of the breaker is removed when not in use. A primary disadvantage of this device is that it fails to permit immediate, unassisted switching from breaker to bucket, and thus simultaneous operation is impossible. Another disadvantage of this device is that it requires manual handling of the extremely heavy chisel tool each time the operator desires to convert to a breaker or bucket operation. Another disadvantage of this device is that it is extremely complex and expensive. Another disadvantage of this device is that it cannot be retrofit to existing excavators.
More recently, a commercially successful solution to at least part of this problem is disclosed in U.S. Pat. No. 6,430,849, U.S. Pat. No. 6,751,896, U.S. Pat. No. 7,117,618 and U.S. Pat. No. 7,257,910 (collectively, “the '849 patent family”). The '849 patent family discloses the Bayonet® Breaker System which provides an excavating machine known as a back-hoe with a specially designed pivotable boom stick assembly that includes a boom stick having first and second excavating tools secured thereto for movement relative to the boom stick. The first excavating tool is an excavating bucket secured to the boom stick for pivotal movement relative thereto between a first position and a second position, and the second tool is a breaker secured to the boom stick for pivotal movement relative thereto between a stowed position and an operative position.
As described in the '849 patent family, the bucket is operable when the breaker is in its stowed position. The bucket is movable by the drive apparatus independent of the breaker, to perform a digging operation. The breaker is operable when the bucket is in a first “stowed” position, which is away from the deployed position of the breaker to prevent contact and interference. The breaker is movable by the drive apparatus independent of the bucket, to perform a breaking operation. Accordingly, the excavating machine may be advantageously utilized to perform both digging and breaking operations without equipment change-out on the boom stick.
However, this solution fails to solve the need for gripping removal objects. Central to the inventions of the '849 patent family is the avoidance of contact and interference of the bucket and the breaker during operation, the independence of their function and operation, and the remote positions provided for allowing independent operation. This is necessary because operating the bucket against the breaker is well-known in the industry to destroy the breaker housing and/or the breaker deployment cylinder.
Another disadvantage is that the '849 patents disclose a hydraulic control circuitry operable to selectively route hydraulic fluid through the hydraulic flow circuit to (1) a first portion of the drive apparatus associated with the bucket, or (2) a second portion of the drive apparatus associated with the breaker. This may prevent interference of the bucket with the breaker, but it is undesirable for a gripping function that benefits from simultaneous operation of the breaker deployment cylinder and the bucket.
The '618 patent suggests using the bucket against a free swinging and unpowered breaker for the purpose of lifting the breaker from a gravity deployed position back into a latched stowed position. This cylinder-less low cost alternative is now known to be unworkable as contact with even an unpowered breaker assembly destroys the breaker housing, and none have ever been made. Further, it is universally found necessary to have independent control over positioning of the breaker. Thus all workable configurations require a lower powered breaker deployment cylinder that is subject to destruction from the crushing force of the much higher powered hydraulic cylinder of the bucket.
The present invention contradicts the core principals of the prior art and practice by providing a combined bucket-gripper-breaker assembly on the end of an otherwise conventional excavator. In this invention, a gripper assembly is constructed around the breaker. The hydraulically powered gripper is then operated in concert with the bucket, intentionally placing the hydraulic power of the bucket and gripper assembly into operable positions of conflict. The reinforced structure of the gripper assembly is not damaged by the force. The gripper's serrated edges grip the removal object. To prevent overload and destruction of the gripper assembly deployment cylinder, a relief valve and accumulator are provided in the gripper's actuator line. Overloading by the bucket activates the relief valve, allowing hydraulic fluid to pass to the accumulator and causing retraction of the gripper, but avoiding destruction of the cylinder. In this manner, the additional functionality of gripping and lifting is provided to the excavating machine. This permits the use of the excavator to grip and lift material excavated by the breaker and bucket that might otherwise be unmovable or difficult to move with the bucket alone.